1. Field of the Invention
The present invention relates to an illumination device and a method of implementing an illumination device in which one holder and the other holder, each holding an optical element, are bonded after their positions are relatively adjusted while measuring the amount of light so as to minimize the amount of light loss which occurs upon optically coupling the optical elements to each other.
2. Description of the Related Art
The technique of relatively aligning a pair of optical elements including an optical fiber and a phosphor while making their optical axes match each other is generally called “active alignment”. In this active alignment, the amount of light transmitting through the optical elements is measured. The optical elements are optically coupled after their positions are relatively adjusted so as to minimize the amount of light loss, that is, temporarily make the optical axes of the optical elements match each other.
An optical element module assembled using the active alignment is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2001-350064.
In Jpn. Pat. Appln. KOKAI Publication No. 2001-350064, a holder that holds an optical fiber (optical element) and a holder that holds an optical element such as a photodiode (PD) are aligned. An adhesive intervenes between the holders and is cured under UV irradiation light, thereby assembling an optical element module.
Active alignment is used when assembling the optical element module. That is, the amount of light is measured, and the positions of the holder including the optical fiber and that including the PD are adjusted in accordance with the measurement result. After that, the adhesive is cured under UV irradiation light to bond the holders. The optical elements are thus optically coupled to assemble the optical element module.
In the active alignment of the optical element module disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-350064 described above, the optical fiber side and the PD side are relatively aligned based on the measurement result. However, the detailed alignment method is not disclosed.
The optical coupling state is affected by external factors such as the angle and finishing accuracy of a V-groove in the PD holder, the angularity and finishing accuracy of the bonding surface of the PD holder, the angle and finishing accuracy of a V-groove in the optical fiber holder, and the thickness of the adhesive. For this reason, the optical coupling state may shift due to these external factors. That is, the optical axis of the optical fiber and that of the PD may be misaligned. If the optical coupling is not ensured as desired, it is difficult to minimize the amount of light loss upon optical coupling.
In addition, if the thickness of the adhesive is uneven, or the whole adhesive is not uniformly irradiated with the UV irradiation light, the holders to be bonded may shift when the adhesive is cured. Even if the optical fiber and the PD are sufficiently optically coupled, the shift of the holders to be bonded may make it impossible to maintain the desired optical coupling state.